The present invention relates to pumping devices. The invention is particularly applicable to portable vacuum-producing machines, and is therefore described below with respect to this application.
Portable vacuum-producing machines are widely used as medical suction pumps, for example in drawing off waste fluids. A common type of medical suction pump now in use includes a cylinder and piston assembly with the piston reciprocated via a crank and piston rod. Reciprocation of the piston produces a vacuum within a sealed container for drawing waste liquids into the container.
Heretofore, medical suction pumps generally employed relatively large motors. This reduces the portability of the pumps and also precludes the use of small portable batteries for operating them. In addition, the known medical suction pumps are generally not capable of operating with several optional power sources, thus reducing their availability as an emergency stand-by medical aid. A further drawback in many of the existing medical suction pumps is the lack of a simple and reliable safety valve arrangement to terminate the suction when the container is full, and thereby to prevent the drawn liquids from entering the pump and contaminating or damaging it.